Re: ROT13 and alike

[Hans Hagen <pragma@wxs.nl>]

At 07:15 PM 2/16/01 +0100, Giuseppe Bilotta wrote:

>ROT13, for those who don't know, is a way to code text by swapping
>the first 13 letters of the latin alphabet with the last 13 letters;
>appling ROT13 to ROT13ed code returns the original message.
>
>This kind of things can be achived with Virtual Fonts, but I don't
>like the approach at all. Also Omega's OCP lists can do similar things.
>Now, I was looking for another approach, working in pure TeX, and came
>to the code snippet in the attached file (actually, che coding it
>applies is not ROT13 but the code of a former Italian secret society,
>"carbonari"; but the idea is similar). It works ... almost.

Given that this secret society is okay i can provide a better solution. 

\starttext

\startmapping[rot13]
  \definecasemaps  65 to  77 lc +13 uc +13
  \definecasemaps  78 to  90 lc -13 uc -13
  \definecasemaps  97 to 109 lc +13 uc +13
  \definecasemaps 110 to 122 lc -13 uc -13
\stopmapping

\def\ToRotThirteen  #1{{\enablemapping[rot13]\lowercase{#1}}}
\def\FromRotThirteen#1{{\enablemapping[rot13]\uppercase{#1}}}

Ecco una prova di alfabeto carbonaro.

\ToRotThirteen{Ecco una prova di alfabeto carbonaro.}

\FromRotThirteen{\ToRotThirteen{Ecco una prova di alfabeto carbonaro.}}

\stoptext

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